Conventionally, a stepping motor for light loads has been well known. But, few cases are known as to the motors which have been practically used for providing a stepping motion to transfer a heavy weight at a high-speed.
Besides, there has been no means for realizing a numerical control in transferring a light load in a high speed condition.
A first problem for a heavy-duty stepping motor for numerically controlling a heavy load is that it tends to become large in size. This further poses the following problems.
(a) Due to its large inertia, it requires a considerably long time to finish one complete stepping motion. Thus, its rotational speed becomes so low that its utility is largely spoiled.
(b) Due to its large output torque, a large electric power is required for obtaining adequate acceleration and deceleration in each stepping motion. Thus, a large energy is consumed but also its efficiency is largely deteriorated to become a substantial drawback to its utility.
A second problem for a heavy-duty stepping motor is that it is required to shorten a stepping angle. However, if teeth are provided on magnetic poles for solving this problem, the rotational speed of the motor will be lowered, and thus an overall control time is too elongated for quick response.
Thus, it is an object of the present invention to provide a numerically controlled load actuating apparatus, which is capable of carrying out a numerical control of a load at a high speed and efficiently.